Driving systems of this kind, more especially having the stated components, are known and have been used in practice in many variations. This applies to stepless gearing types as well as to the various methods for boosting the engine. Each of the known versions has, however, also specific disadvantages.
Stepless transmissions which have the advantage e.g. of keeping the driving torque at a maximum and keeping the fuel consumption to a minimum face the fundamental problem that a change in the speed ratio of two shafts is in principle possible only with a temporary or permanently-partial interruption of the power transmission between them. The degree of slippage upon transmission changers gives rise to specific disadvantages in the mechanical and hydraulic types of stepless transmissions in accordance with the prior art, be they defined or undefined slippage intervals of the mechanical or hydraulic type. Even pneumatic transmissions could be said to fall within this category.
Special compressed-air transmissions using displacement effect, for example for tools or for lifting appliances, are known which are driven by compressed air. They are of no use in driving systems having internal combustion engines. On the other hand, a pneumatic transmission having several propellers, a turbine and circulating air flow for power transmission is disclosed in German Offenlegungschrift No. 1,945,905. However, with undefined, permanent slippage, the efficiency and maximum transferrable torque thereof are rather poor.
A further example proposed in German Patent Specification No. 920,220 is a unit which generates compressed air for boosting the engine, with the object of increasing the throughput of air in the combustion chambers thus raising the performance and reducing the fuel consumption. The use of such units have specific disadvantages. For example, mechanical superchargers having compressors of the displacement type, directly driven by the crankshaft, utilize a relatively high proportion of the useful power. Moreover, exhaust gas superchargers, for example pressure-wave and turbo superchargers, which operate with the energy of the exhaust gas, work under considerable thermal load and are very dependent on engine speed. All the known supercharger systems have in common the fact that they consume energy and are operated independently of the power transmission. The problem of driving systems involving internal combustion engines, is one of converting the limited range of favourable engine speed to a such greater range of speed of the driving shaft, and this subject is not dealt with by the prior art proposals.